The firm that designed the new Bay Bridge eastern span warned Caltrans as the bridge neared completion that some of its welds could crack prematurely under the constant pounding of cars and trucks, The Chronicle has learned.

The potential for cracking was created after the span was designed, said engineers with the firm T.Y. Lin International. It happened when Caltrans suspended its rules and allowed the bridge builder to weld together Chinese-manufactured sections of steel road deck that didn't fit together correctly.

Any cracks in the welded connections would be minor, the engineers concluded, and would not pose the threat of a catastrophic failure. However, such cracking could shorten the time before toll-payer dollars would be needed to make repairs to the $6.4 billion bridge.

The engineers also told Caltrans and other bridge project officials that in a major earthquake there would likely be some damage to the ill-fitting joints.

In their November 2010 evaluation, the T.Y. Lin engineers identified a section of the eastbound deck near Yerba Buena Island as being of particular concern, because lopsided welded connections are under high stress and thus are especially vulnerable to premature cracking. The Chronicle obtained the firm's report under the state Public Records Act.

Downplaying risk

Caltrans officials said last week that the risk of cracking is remote and that they had to balance the possibility against the cost and potential complications of trying to repair the misaligned deck sections.

Critics said Caltrans' actions undermined the span's status as a lifeline after an earthquake - a road intended to be open for emergency vehicles and trucks within a day - and could shorten its predicted 150-year life span.

"What they've apparently done is rationalized the acceptance of excessive fatigue damage at these locations," said Bob Bea, a professor emeritus of civil engineering at UC Berkeley. "For a lifeline bridge, this is a maintenance nightmare."

At the root of the problem are the Chinese-made deck sections that make up the suspension portion of the span. The 10 sections, each 90 feet wide and 120 feet long, were fabricated at a plant in Shanghai and initially fit together correctly when checked on the factory floor.

When they were brought to the bridge construction site in early 2010 and suspended in the air, however, the sections no longer fit together the same way. Some were off by a quarter of an inch, nearly half the thickness of the steel plates being joined.

Caltrans rules forbid bridge decks from being joined together if they are off by more than an eighth of an inch, because of the heightened stress that puts on the welds. The added stress also violates Caltrans' limits aimed at preventing cracking.

When confronted with the problem, Caltrans' chief engineer, Brian Maroney, said builders could use laxer stress-level standards set by a national group, the American Association of State Highway and Transportation Officials, instead of the state guidelines.

"When it comes to steel fatigue, quite frankly, the greater United States has a tremendous amount of knowledge," Maroney said in an interview. "In my professional judgment, I didn't think it was worth it to drag public dollars into a battle with national experts.

State standards higher

"I respected the ... national standards above California standards for those reasons," Maroney said. "I was balancing state dollars versus was it worth doing battle with experts?"

But Martin Pohll, a retired Caltrans structural steel expert who served on the agency panel that sets California's guidelines, said the state intentionally kept its standards higher than the national group's.

"If something is working, you usually don't change it. That was kind of the consensus," Pohll said.

Maroney acknowledged that, in some spots, the bridge falls short even of the national group's weaker standards. But said he was prepared to make the trade-off.

"I looked at it and said, 'OK, we could cut it out and remelt the steel, rework the steel,' " he said. "In this case, is the cure worse than the disease?"

Top officials from Caltrans, as well as its seismic peer review panel and bridge consultants, gathered for a briefing about the ill-fitting sections in October 2010.

In a verbal presentation, T.Y. Lin's chief bridge designer, Marwan Nader, and consultants hired by the bridge's main contractor, the joint venture American Bridge/Fluor, said it was unlikely the welds would crack from traffic alone, according to minutes of the meeting.

Key meeting

When Nader's firm presented its report a month later, however, it cautioned, "It should be noted that the deck plate (near Yerba Buena Island) may sustain some fatigue damage," resulting in "reduced fatigue life."

In addition, the engineers said, welds on roughly half of the eastbound deck and a quarter of the westbound deck probably had excessive stress levels that didn't conform to Caltrans' standards.

Checking those areas for problems as the years go on will be difficult, because steel bars that bridge workers had to leave in place under the welds to make the joints hold together block views of the welds.

The welding episode was not the first time Caltrans suspended its standards on the Bay Bridge project. Hundreds of galvanized steel rods and bolts that hold together the signature tower, seismic-stability structures and other features of the span were manufactured to levels harder than Caltrans normally allows on bridges, a factor that may have left them more vulnerable to being invaded by corrosive marine air.

32 fasteners snapped

Thirty-two of the fasteners snapped after they were tightened last year. Caltrans is still doing tests to see if more rods or bolts could be at risk.

Some experts questioned Caltrans' decision to go with the more lax standards on the welds.

Roumen Mladjov, a structural engineer who sat on the design panel for the project in 1998, said the stresses on the deck outlined in the T.Y. Lin report were "very disturbing."

He said he was especially alarmed that the backing bars had been left in place under the welds, not just because they prevent visual checks, but because they add to already elevated stress levels on the road deck's joints.

'Start repairing'

"It's absolutely unacceptable what they are saying and what they are doing," Mladjov said. "If this is true what they put there, they need to immediately investigate and start repairing the whole thing.

"Nature will find the most vulnerable points," he said. "This will crack, absolutely. If it starts cracking, that's a major problem."

Maroney said he expects the bridge will have to be regularly checked for cracking simply because it is a steel bridge. He added that the minor risk was worth it. "Nothing in the world is perfect - you have to be realistic," he said. "This is a great bridge. I feel good about the call."

Problems with eastern span

The new eastern span's ill-fitting steel deck sections are only one source of concern on the $6.4 billion project. Among the others:

-- During storms, water leaks into steel structures that support the roadway on the suspension span. The source of the leaks is unclear - possibilities include holes drilled for electrical conduits and problems in the drainage system for the safety guardrails that sit atop the bridge's deck.

-- Large rods and bolts made of high-strength, galvanized steel may be at risk of cracking. Thirty-two rods snapped last year on a seismic stability structure on the suspension span. They failed after being exposed to the elements for more than five years. Caltrans is doing tests to determine whether more than 2,000 other rods and bolts could similarly crack. The rods and bolts are found on the top and in the base of the tower and anchor the main cable.

-- Hundreds of welds holding together steel deck sections of the suspension span were found to be defective when they were inspected at a manufacturing plant in China. Caltrans said the welds were repaired and passed muster before they arrived on site.

-- Design flaws, corrosion, fabrication errors and snapped bolts dogged construction of the still-incomplete bike path, leading to at least $3.8 million in cost overruns.